In a dental clinic, caries treatments are carried out by eliminating caries parts from tooth to form cavities, and by filling composite resin after applying a dental adhesive to the cavities. However, when adhesion properties of these materials are insufficient, there are problems such as dental pulp stimulation, secondary caries, detachment of composite resin and the like.
Conventionally, as a dental adhesive, a one liquid-type self-etching primer, a one-liquid type one-step bonding agent and the like which comprise essentially adhesive monomers such as a (meth)acrylate monomer having intramolecularly an acidic group have been proposed and produced. However, there are problems such as hydrolysis of ester bonds of the (meth)acrylate monomers in a strong acidic solution, deterioration of adhesion properties by hydrolysis at an adhesion interface between an adhesive and tooth substances and the like.
Recently, many manners on (meth)acrylamide monomers having an acidic group for excluding unstable factors in adhesion properties are disclosed.
Macromolecule Chemistry Physics vol. 200, pp. 1062-1067 (1999) reports that a phosphonic acid group-containing monomer having no ester bond prevents adhesion deterioration caused by hydrolysis and improves shelf lives of products.
JP 2003-89613A and Journal of Dental Research, Vo. 83. Special Issue No. #2661 report that a self-etching primer comprising N-methacryloyl-ω-aminoalkylphosphonic acid and N-methacryloyl glycin prevents adhesion properties from deterioration caused by hydrolysis.
However, while N-methacryloyl-ω-aminoalkylphosphonic acid, for example, N-methacryloylaminoethylphosphonic acid is excellent in hydrolysis stability when used in an aqueous primer, it has a defect not to solve into hydrophobic resin.
Recently, many adhesive monomers are reported which is characterized by so-called anti-hydrolysis stability. Such adhesive monomers are disclosed in JP 2006-176511A, JP 2006-176522A, JP 2006-199695A, JP 2006-514114A, and JP 2006-520344A and the like.
Among them, since the compounds disclosed in JP 2006-176511A, JP 2006-176522A and JP 2006-520344A have intramolecularly a phosphate group, they have a risk in which their C—O—P bonds are hydrolyzed.
Regarding the compounds disclosed in JP 2006-199695A and JP 2006-514114A, anti-hydrolysis stability can be expected but solubility in water and hydrophobic resin is problematic.
As discussed above, although a variety of adhesive monomers have been proposed to date in order to solve the problem that adhesion properties deteriorate due to reduction of shelf lives of products caused by hydrolysis in aqueous self-etching primers and dental one-liquid type one-step bonding agents, they are not satisfactory.